The long-term goal of the research in Caro-Beth Stewart's laboratory is to understand the molecular basis for adaptive evolution of higher organisms, such as humans. That is, the research is aimed at understanding how changes in DNA and protein sequence are responsible for observed differences between species. To address this large goal, Stewart's current research primarily focuses on the regulatory and structural/functional evolution of digestive enzymes in animals with different diets. The digestive tract is an ideal place to look for evidence of adaptive evolution because the gut mucosa contacts the external environment, and diets can shift rapidly due to environmental or behavioral changes. The gut is genetically plastic, showing morphological adaptations to the diet of a species and expression of relevant digestive enzymes in different regions. A change in the expression pattern of an enzyme can place it under new selection pressures, which may drive the evolution of its primary structure and function. This research will help elucidate how organisms adapt genetically to environmental change. In addition, it will give insight into changes that are allowed in protein sequence, structure,